Alzheimer's disease afflicts more than four million people in the United States, and this number is expected to double during the next forty years with the aging of the population. After heart disease, cancer, and stroke, Alzheimer's disease is the fourth leading cause of death among the elderly in developed nations. Alzheimer's disease is a complex multi-genic neurodegenerative disorder characterized by progressive impairments in memory, behavior, language, and visuo-spatial skills, ending ultimately in death. Hallmark pathologies of Alzheimer's disease include granulovascular neuronal degeneration, extracellular neuritic plaques with beta-amyloid deposits, intracellular neurofibrillary tangles and neurofibrillary degeneration, synaptic loss, and extensive neuronal cell death. It is now known that these histopathologic lesions of Alzheimer's disease correlate with the dementia observed in many elderly people.
Although Alzheimer's disease is one of the most common types of dementia among the elderly, it is difficult to diagnose because Alzheimer's-like symptoms are common to many other diseases (e.g., AIDS, brain cancer, Parkinson's disease, and deficiencies of vitamin E, magnesium, and B vitamins). Generally, the only definite diagnosis comes from a postmortem biopsy of the diseased brain.
Over one hundred billion dollars are spent annually on Alzheimer's disease, making it the third most costly disease in the United States after heart disease and cancer. Much of this cost is related to caregiving, such as nursing home care and in-home day care. Accordingly, to the extent Alzheimer's disease could be affirmatively diagnosed during an individual's lifetime, medical treatment might be provided that might provide benefits by slowing the rate of cognitive decline, delaying institutionalization, reducing caregiver hours, and improving quality of life.
Early detection and identification of Alzheimer's disease is necessary to facilitate prompt, appropriate treatment and care. Currently, there is no laboratory diagnostic test for Alzheimer's disease. As stated above, the only true existing diagnosis is made by pathologic examination of postmortem brain tissue in conjunction with a clinical history of dementia. This diagnosis is based on the presence in brain tissue of neuritic (senile) plaques and of neurofibrillary tangles, which have been correlated with clinical dementia. The neurohistopathologic identification and counting of neuritic plaques and neurofibrillary tangles requires staining and microscopic examination of several brain sections. However, the results of this methodology can vary widely and is time-consuming and labor-intensive.
Thus, there remains a need for diagnostic methods for Alzheimer's disease. In particular, reliable and cost-effective methods and compositions are needed to allow for diagnosis of Alzheimer's disease.